Engines, including diesel engines, gasoline engines, gaseous fuel powered engines, and other engines known in the art exhaust a complex mixture of air pollutants. These air pollutants can include gaseous compounds, such as the oxides of nitrogen, and solid material known as particulate matter or soot. Particulate matter is commonly removed from engine exhaust streams using a device known as a particulate filter. Particulate filters typically include a porous filtration medium that traps particulate matter and permits other exhaust gas constituents to flow through. After a period of time, particulate filters become clogged with particulate matter, which must be removed in order for the particulate filter to continue functioning properly. The process of removing particulate matter from a particulate filter is known as regeneration. Particulate filter regeneration methods commonly include steps of detecting when a particulate filter has reached a maximum capacity, artificially raising an exhaust temperature to a high enough temperature to combust particulate matter, and maintaining that temperature until a sufficient amount of particulate matter has been burned away.
Known methods for detecting when a particulate filter has reached maximum capacity have included calculating a particulate load of the particulate filter using various inputs, including a pressure differential across the particulate filter, particulate filter temperature, time spent at various throttle notch settings, time spent at idle, and time since a previous regeneration. Also, known methods of achieving and maintaining regeneration temperatures have included increasing throttle notch settings for predetermined periods of time. However, these methods may not be optimum.
An exemplary exhaust system that artificially raises the temperature of exhaust passing through a filter is disclosed in U.S. Patent Publication 2013/0046424 of Gallagher et al. that published on Feb. 21, 2013 (“The '424 publication”). Specifically, the '424 publication discloses a locomotive having a diesel engine connected to an exhaust system that includes a particulate filter. A locomotive controller communicates with the engine, a throttle, and a consist controller. The locomotive controller receives signals from various engine sensors to determine when to regenerate the particulate filter. The locomotive controller and consist controller adjust load distributions among locomotives in the consist to generate higher exhaust temperatures for assisting regeneration. Throttle notch settings are adjusted in each locomotive to assist regeneration of a particular locomotive's particulate filter. Regeneration is determined to be complete based on sensor data or after a certain amount of time has passed, such as 30 minutes.
Although the system of the '424 publication may adequately regenerate an exhaust particular filter, it may still be less than optimal. Specifically, the system may not consider important operating conditions of the diesel engine and exhaust system prior to and/or during regeneration that could improve an efficiency of the regeneration process. Particularly, the system may not account for ash content separately from soot content within the particulate filter, which may lead to inaccurate triggering and/or termination of regeneration. Further, throttle notch settings may not be effectively managed to improved efficiency and reduce damage to the particulate filter during the regeneration process.
The disclosed exhaust system addresses one or more of the problems discussed above and/or other problems of the prior art.